Synthetic resins have found a variety of applications due to their excellent processing and application-technological properties. However, except for halogen-containing resins, such as polyvinyl chloride and poly(tetrafluoroethylene) which are self-extinguishing, synthetic resins typically are flammable and support flaming combustion. For the purpose of overcoming this disadvantage, the resins are usually admixed with fire-retardant additives, the most common thereof being compounds which contain halogen, phosphorous and antimony. At elevated temperatures, these compounds split off their respective acids which effectively inhibit a continuation of flaming combustion.
In regard to the voluminous pertinent patent literature in this area, the following patents shall be cited as examples, e.g., German (OS) 15 69 123 disclosing antimony oxychloride as a fire-retardant additive and German (OS) 14 94 922 disclosing the addition of phosphine and phosphoric acid compositions.
However, fire retardants capable of splitting off an acidic compound have the obvious disadvantage that such acids are corrosive, thus possibly causing damage or destruction of electrical or electronic components, including electrical cables. Furthermore, it should be mentioned that resins rendered flame-retardant in such a manner will typically generate a considerable amount of smoke which will obviously interfere with fire-fighting and rescue operations. Besides, as determined in more recent studies, the combustion products of flame-retardant resins exhibit a considerable degree of toxicity.
According to German Patent 27 39 429, attempts have been made to resolve these disadvantages by adding an inorganic magnesium compound, an alkali chloride and an inorganic tin or vanadium compound to the synthetic resin. Besides the fact that tin and vanadium compounds represent a significant cost factor, the presence of alkali chloride, which is necessary for achievement of satisfactory flame-retardancy, cannot entirely eliminate the aforementioned disadvantages. The use of borates as flame-retardant additives has been described in the German (AS) 17 69 312. Admittingly, borates do not form a corrosive acid, but the flame-retardant effect therefrom is relatively weak, requiring the addition of another fire-retardant agent, such as antimony oxide.
Finally, German (OS) 28 09 294 should be mentioned, wherein the use of aluminum hydroxide as a halogen-free flame-retardant is described for copolymers of polyolefins and synthetic rubbers, using, as the case may be, a combination of magnesium carbonate. However, only those types of synthetic resins which permit incorporation of fillers and additives on a roller-mill can be used for admixing, without difficulties, the necessary large amounts of these flame-retardant additives.
Due to the non-availability of a suitable flame-retardant for molded plastic cable splices, such types of cable connections cannot be used in critical areas, in particular in electrical and electronic devices. Therefore, with reference to new installations, the result is that excessive lengths of cable will be consumed and, even more serious, no repair work is possible if cable damage occurs. The entire length of the damaged cable has to be replaced. Such an excessively high cable consumption is, however, uneconomical and cannot be justified.
Therefore, the present invention deals with the preparation of a cast cable connection consisting of a plastic wrapping and a molded cable splice comprising synthetic resins. This cable connection will not form corrosive products when exposed to fire and will not generate toxic by-products of combustion, but the fire-resistance thereof will be at least equal to that of resins prepared with halogen-containing fire-retardant additives. In case of fire, the cable connection will retain its function over a sufficiently long period of time.